A viewpoint in The Structural Engineer (2 November 1993) gave the views of Dr Menzies as Secretary of the Standing Committee on Structural Safety (SCOSS) on ‘Improving structural safety through feedback’. Whilst I agree with the views expressed in the article, and that it is valuable to obtain feedback from engineers who have encountered failures or potential failures, I feel that there is another feedback mechanism which remains largely untapped but which could prove valuable, especially as the use of computers in design and analysis is increasing. The feedback mechanism is simply one of taking measurements of the overall characteristics of a structure when it has been constructed and comparing the measurement with the equivalent characteristic assumed in design. The parameter which should be used for the comparison is the fundamental natural frequency, and the reason for using the frequency is that it is both easy to measure and it also relates to the stiffness and mass of the structure which are two key parameters in design. I realise that engineers rarely calculate natural frequencies, but they will have all the information from their
design which would allow them to do so, and this could include all the assumptions and simplifications adopted.